1. Field of the Invention
The present invention relates to a non-contact charger and a non-contact charging system which prevent a metallic foreign matter such as a coin from being heated.
2. Discussion of Related Art
There is known a non-contact charger which charges an equipment that is placed therein so as to be charged. In the non-contact charger, the placed equipment is charged with electricity by transmitting a magnetic flux energy (electromagnetic induction energy). When a metallic foreign matter such as a coin is placed in the non-contact charger, the foreign matter is heated by an eddy current. In order to prevent the foreign matter from being heated, a technique has been developed, which detects whether the equipment to be charged or the foreign matter is placed in the non-contact charger.
For example, Patent Document 1 (JP-A-2002-34169) discloses an non-contact charger in which a mobile phone as the equipment to be charged is arranged to change a charging load according to a predetermined pattern upon placement of the mobile phone for initiation of charging. The non-contact charger keeps generating the magnetic flux energy that is enough to charge the mobile phone only when the non-contact charger detects a change of the charging load according to the predetermined pattern during a predetermined time period. On the other hand, in a case where the foreign matter such as the coin is placed in the non-contact charger, it is impossible that the non-contact charger detects such a charging load change according to the predetermined pattern during the predetermined time period. Thus, it is apparent that the foreign matter instead of the mobile phone is placed in the non-contact charger, so that heating of the foreign matter is prevented by means that the non-contact charger generates an imperceptible volume of the magnetic flux energy or stops a generation of the magnetic flux energy.
However, in order that the mobile phone changes the charging load according to the predetermined pattern and the non-contact charger detects the change of the charging load, the mobile phone and the non-contact charger need to incorporate respective circuits having complicated structures.